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An honest approach to Filtration

You need filtration because...
The typical garden pond has an unacceptably high concentration of fish (producing ammonia and nitrite) when compared to lakes, rivers and other natural habitats unless a suitable filtration system is installed. Nature achieves a balance by restricting the number of fish in relation to the available surface area. The way to overcome this is with an efficient filtration system. After all, one fish per garden pond would look boring!

A garden pond is a closed environment and there is no way for the fish waste to leave the pond. If the waste is not filtered the fish are left to swim in their own sewage. It is not always obvious when a pond has a dangerously high level of toxic waste. It is possible to have what appears to be clear water in your pond but one in which fish will not live. It may be so full of clear toxins that even algae is unable to live in the water. What chance do the fish have?! Bleach is clear and yet you would not expect your fish to live in it! Unless your filter is capable of filtering the entire water contents of your pond approximately every two hours it is unlikely to keep your pond in a healthy condition. When you first stock your pond the level of filtration needed will probably be much less than that required in later years. Fish grow! As they grow they require more food and therefore produce more waste! Unless you plan well ahead your filter may not give adequate performance in the future. If your filtration system has been running for a few years ask yourself.....

How many additional fish have you added to the pond?
If they have grown, how much larger have they grown, how much more are they eating and how much additional waste are they producing? This puts additional pressure on your system.
If they have not grown, is it because your filtration system is no longer adequate (size DOES matter)?
When did you last check the efficiency of your filter?
What are your nitrate and ammonia levels?

Where do we start?....
Pond size! First... we need to establish the size of the pond to calculate its gallonage. Unless we get this right everything else will be a waste of time. The size of the pond governs the amount of water to be filtered.

How do we calculate this?
The diagrams below show a simple way to assess the volume of an irregular shape by breaking it down into smaller sub units.

In this example the pond has been divided in two main sections A and B. Measure each section in feet. All figures should be rounded UP to the nearest whole foot. For filtration purposes you would be better to over estimate the volume. (This only applies to filtration calculations and NOT for medication. It is GOOD to over filter but BAD to over medicate). The volume of each section is calculated using length x width x depth. This gives us an answer in cubic feet. Each cubic foot holds 6¼ gallons of water. The volumes of the two sections (A & B) should then be added together to give the total cubic capacity. This is multiplied by 6.25 to give the total volume in gallons.